• Korean Journal of Fisheries and Aquatic Sciences
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• v.51 no.1
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• pp.107-112
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• 2018

One-dimensional numerical model is implemented to investigate temperature variations in the mixed layer depth (MLD) with the passage of typhoons. In the model, we assume a non-divergent, infinite ocean and consider wind effects only, excluding isostatic effects (inverse barometric effects) and upwelling with vertical movement of the water column. Numerical experiments investigate the effects of typhoon tracks on temperature variations, including their dependence on vertical resolutions in the MLD and these results are compared with those in a three-dimensional primitive equation model (POM). The model reproduces features of the observed temperature variations in the MLD fairly well, and implies that wind effects, rather than isostatic effects, play a predominant role in temporal and spatial temperature variations in the MLD. After the passage of typhoons, however, the model does not reproduce well the temperature variations observed in the MLD, because a limitation of the model is its inability to reproduce events such as cyclonic eddy formation (Hong et al., 2011; Masuda and Hong, 2011). The model also shows well the so called 'rightward bias' (Price, 1981) of sea surface cooling which is the most predominant in the right hand side of typhoon's track.

• Journal of Environmental Science International
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• v.13 no.10
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• pp.891-902
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• 2004

In order to predict air pollution and Yellow-sand dispersion precisely, it is necessary to clarify the sensitivity of meteorological field input interval. Therefore numerical experiment by atmospheric dynamic model(RAMS) and atmospheric dispersion model(PDAS) was performed for evaluating the effect of temporal and spatial resolution of meteorological data on particle dispersion. The results are as follows: 1) Base on the result of RAMS simulation, surface wind direction and speed can either synchronize upper wind or not. If surface wind and upper wind do not synchronize, precise prediction of Yellow-sand dispersion is strongly associated with upwelling process of sand of particle. 2) There is no significant discrepance in distribution of particle under usage of difference temporal resolution of meteorological information at early time of simulation, but the difference of distribution of particles become large as time goes by. 3) There is little difference between calculated particles distributions in dispersion experiments with high temporal resolution of meteorological data. On the other hand, low resolution of meteorological data occur the quantitative difference of particle density and there is strong tendency to the quantitative difference.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2744-2749
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• 2008

Numerical calculations are carried out for the natural convection induced by temperature difference between a cold outer square cylinder and a hot inner circular cylinder for Rayleigh number of $Ra=10^7$. This study investigates the effect of the inner cylinder location on the heat transfer and fluid flow. The location of inner circular cylinder ($\delta$) is changed vertically along the center-line of square enclosure. The natural convection bifurcates from unsteady to steady state according to $\delta$. Two critical positions of ${\delta}_{C,L}$ and ${\delta}_{C,U}$ as a lower bound and an upper bound are ${\delta}_{C,L}=0.05$ and ${\delta}_{C,U}=0.18$, respectively. Within the defined bounds, the thermal and flow fields are steady state. When the inner cylinder locates at ${\delta}{\geq}{\delta}_{C,U}$, the space between the upper surface of inner cylinder and the top surface of the enclosure forms a relatively shallow layer where the natural convection characterized as the pure Rayleigh-Benard convection forms alternately the upwelling and downwelling plums, as a result that a series of cells known as Benard cells is derived.

• 한국지구과학회:학술대회논문집
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• 2005.09a
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• pp.124-131
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• 2005

A GDS (Geomagnetic Depth Sounding) method, one of extremely low-frequency EM methods, has been carried out to examine deep geo-electrical structures of the Korean peninsula. In this study, five additive GDS sites acquired in south-eastern area of the Korea were integrated into twelve previous GDS results. In addition, 3-D MT modeling considering the surrounding seas of the Korean peninsula was performed to evaluate sea effect at each GDS site quantitatively. As a result, Observed real induction arrows was not explained by solely sea effect, two conductive structures that are able to explain differences between observed and calculated induction arrows, was suggested. The first conductive structure is the Imjingang Belt, which is thought as a extension of Quiling-Dabie-sulu continental collision belt. The effects of the Imjingang Belt clearly appear at YIN and ICHN sites. The second one is the HCL (Highly Conductive Layer), which is considered as a conductive anomaly by mantle upwelling generated in back-basin region. The effects of the HCL are also confirmed at KZU, KMT101, 107 sites, in the south-eastern of the Korean peninsula.

• Korean Journal of Ecology and Environment
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• v.41 no.4
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• pp.472-484
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• 2008

The calibrated Andong Reservoir hydro-dynamic module (PART I) of the 2-dimensional hydrodynamic and water quality model, CE-QUAL-W2 [v3.2], was applied to examine the dynamics of total phosphorus, and chlorophyll $\alpha$ concentration within Andong Reservoir. The modeling effort was supported with the data collected in the field for a five year period. In general, the model achieved a good accuracy throughout the calibration period for both chlorophyll ${\alpha}$ and total phosphorus concentration. The greatest deviation in algal concentration occurred on $10^{th}$ October, starting at the layer just beneath the surface layer and extending up to the depth of 35 m. This deviation is principally attributed to the effect of temperature on the algal growth rate. Also, on the same date, the model over-predicts hypolimnion and epilimnion total phosphorus concentration but under-predicts the high concentrated plume in the metalimnion. The large amount of upwelling of finer suspended solid particles, and re-suspension of the sediments laden with phosphorus, are thought to have caused high concentration in the epilimnion and hypolimnion, respectively. Nevertheless, the model well reproduced the seasonal dynamics of both chlorophyll a and total phosphorus concentration. Also, the model tracked the interflow of high phosphorus concentration plume brought by the turbid discharge during the Asian summer monsoon season. Two different hypothetical discharge scenarios (discharge from epilimnetic, and hypolimnetic layers) were analyzed to understand the response of total phosphorus interflow plume on the basis of differential discharge gate location. The simulated results showed that the hypolimnetic discharge gate operation ($103{\sim}113\;m$) was the most effective reservoir structural control method in quickly discharging the total phosphorus plume (decrease of in-reservoir concentration by 219% than present level).

• Journal of Environmental Science International
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• v.24 no.12
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• pp.1657-1671
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• 2015

In this study, the wind direction and the wind speed of the nearest temperature observations point of the National Weather Service was analyzed in order to investigate the rapid rise and drop of water temperature in the East Coast appeared after passing of the 2015 typhoon No. 9 and 11. Then the figures were simulated and analyzed using the WRF(weather research and forecast) model to investigate in more detailed path of the typhoon as well as the changes in the wind field. The results were as follows. A sudden drop of water temperature was confirmed due to upwelling on the East coast when ninth typhoon Chanhom is transformed from tropical cyclones into extra tropical cyclone, then kept moving eastwards from Pyongyang forming a strong southerly wind after 13th and this phenomenon lasted for two days. The high SST(sea surface temperature) is confirmed due to a strong northerly wind by 11th typhoon Nangka. This strong wind directly affected the east coast for three days causing the Ekman effect which transported high offshore surface waters to the coast. The downwelling occurred causing an accumulation of high temperature surface water. As a results, the SST of 15m and 25m rose to that of 5m.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.23 no.6
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• pp.417-424
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• 1990

Effect of physical processes on the surface distributions of chlorophyll-a and nutrients was investigated in the southern sea of Korea during summer season. The northwestern area of Cheju Island had higher concentrations of the chlorophyll-a and nutrients than its southeastern area. A nutrient-rich patch was observed in the western area of Cheju Island and the northern area of $34^{\circ}N$ respectively. It seems that the patch in the western area of Cheju Island is formed by horizontal extension of the low-saline Coastal Water of China Contiental(CWCC), while the patch in the northern area of $34^{\circ}N$ by vertical mixing. Also, the high chlorophyll-a in the vicinity of Cheju Island appears to be ascribed to sufficient supply of nutrient from bottom water by coastal upwelling.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.1
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• pp.59-66
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• 2013

When the typhoons are passing over the ocean, the ocean environment has both physical and biological impacts on the East, South sea and Yellow sea of Korea. As a result of typhoon path, vertical mixing and upwelling injured colder subsurface water, and leaded to phytoplankton blooming along the typhoons. The ocean environment before and after a typhoon played an important role in the biological effect of sea surface. Although the magnitude of sea surface temperature (SST) gets cooler because of typhoon path, other physical and biophysical responses are quite different such as chlorophyll, K490 and SST. The purpose of this study is to compare with the typhoon path that influenced the Korean Peninsula and ocean environment parameters which were observed by ocean color remotely-sensed data. The MODIS data were used to assess the parameters of ocean environments such as K490 and chlorophyll data from 2002 to 2005. Mean chlorophyll from MODIS data increased by about 1-4% in the East sea after the typhoon. Mean concentration of MODIS chlorophyll in the post-typhoon period increased along the typhoon passage. However, Jeju coastal area has different patterns from those of the East sea.

• Ocean Science Journal
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• v.42 no.2
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• pp.103-116
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• 2007

Seasonal changes of tide signal(s), temperature, salinity and current were studied during the years 2004-2005 in the northernmost Gulf of Aqaba, which is under developmental activities, to obtain scientific bases for best management and sustainability. Spectrum analysis revealed permanent signals of tide measurements during all seasons, which represented semidiurnal and diurnal barotropic tides. The other signal periods of 8.13, 6.10-6.32, 4.16 and 1.02-1.05 h were not detected in all seasons, which were related to shallow water compound and overtides of principle solar and lunar constituent and to seiches generated in the Red Sea and the Gulf of Aqaba. Spatial and temporal distribution of temperature, salinity and density showed significant differences between months in the coastal and offshore region and no significant differences among the coastal sites, between the surface and bottom waters and between coastal and offshore waters. Therefore, the temporal and spatial variation of water properties in the northernmost Gulf of Aqaba behave similarly compared to other parts. The coastal current below 12 m depth was weak $(3-6\;cms^{-1})$ and fluctuated from east-northeastward to west-southwestward (parallel to the shoreline), which may be related to the effect of bottom topography and/or current density due to differential cooling between eastern and western parts in the study area, and wind-induced upwelling and downwelling in the eastern and western side, respectively. The prevailing northerly winds and stratification conditions during summer were the main causes of the southward current at 6 and 12 m depths with average speed of 28 and $12cms^{-1}$ respectively.

• Journal of Astronomy and Space Sciences
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• v.30 no.4
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• pp.231-239
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• 2013

To identify seasonal and latitudinal variations of F2 layer during magnetic storm, we examine the change of daily averages of foF2 observed at Kokubunji and Hobart during high (2000~2002) and low (2006~2008) solar activity intervals. It is found that geomagnetic activity has a different effect on the ionospheric F2-layer electron density variation for different seasons and different latitudes. We, thus, investigate how the change of geomagnetic activity affects the ionospheric F2-layer electron density with season and latitude. For this purpose, two magnetic storms occurred in equinox (31 March 2001) and solstice (20 November 2003) seasons are selected. Then we investigate foF2, which are observed at Kokubunji, Townsville, Brisbane, Canberra and Hobart, Dst index, Ap index, and AE index for the two magnetic storm periods. These observatories have similar geomagnetic longitude, but have different latitude. Furthermore, we investigate the relation between the foF2 and the [O]/[$N_2$] ratio and TEC variations during 19-22 November 2003 magnetic storm period. As a result, we find that the latitudinal variations of [O]/[$N_2$] ratio and TEC are closely related with the latitudinal variation of foF2. Therefore, we conclude that the seasonal and latitudinal variations of foF2 during magnetic storm are caused by the seasonal and latitudinal variations of mean meridional circulation of the thermosphere, particularly upwelling and downwelling of neutral atmosphere during magnetic storm.